I have created a solution package using the makecab tool that contains a feature and a DLL which will be installed on the GAC. Its getting deployed globally however I want to deploy it for specific webapplication, what is the change required.
I think there are a couple of ways to force a solution to install to a specific web app.
One way is to have the DLL deployed to the bin directory instead of to the GAC. Beware though, that all API calls will need to be cleared through Code Access Security policies written and placed in your manifest.xml.
Another is to include SafeControls which reference your DLL within the manifest.xml. This means that a web.config will have to be written to, making deployment require a web application to be specified.
Here are scripts to deploy to specific site collections on a web application.